Help: protect /web (site) folder with user and password

Hi, I want to know how to protect /web folder (/var/www/clients/clientXX/webXX/web) with user and password. I've tried using Folder Protection (Folder | Folder users), creating user "test" and password "test", but access to the web site is not secure.

Hi Falko,
in Folder protection, specifying the folder "/", the site is protected and requests a username and password, but if I want to protect a subdomain (for example shop.domain.tld) the panel does not create the subfolder and, therefore, do not protect subdomain.
Why?

I've just checked - it is not possible to select a subdomain in the Website field under Sites > Protected Folders, so I guess I'm not fully understanding what the problem is. Can you describe it in more detail?

Falko,
I think I have understood the problem. When I create a sub-domain, the panel does NOT create the appropriate folder, and then I can not protect it (obviously).
To do this I solved by reading this simple guide here http://docs.ispconfig.org/creating-web-sites/subdomains/ and creating the sub-domain as the domain ... Simple!
Thanks for everything.
Alex